Commercially, it is highly desirable for an electronic display to be as thin and light as possible while still maintaining a high degree of ruggedness and imperviousness to forces that are a consequence of shock and drop. In the area of mobile electronics, such as cellular telephones, personal digital assistants (PDAs), and the like, size and weight are critical factors to the commercial success of a product. However, breakage of the electro-optic displays within these devices remains the primary cause of repairs and product returns.
In general, electro-optic displays contain an electro-optic material having an optical state that changes as a function of an applied electric or magnetic field. The electro-optic material can be contained on a single substrate or can form an electro-optic layer between two substrates that are bonded together. Traditionally, electro-optic displays have been manufactured using glass substrates, making the product heavy, rigid and prone to breakage. Lighter, thinner displays employing rigid plastic substrates also require structural support and shock absorption properties to prevent or reduce breakage. Therefore, attention in the industry has turned to the need for electro-optic displays that are thin and lightweight and can also be bent or flexed while maintaining desirable durability.
There are many useful applications for such flexible products. For example, so-called xe2x80x98electronic paperxe2x80x99 in which fiber paper is replaced with a display would be much more compelling as a product if the electro-optic display could be rolled up or folded like traditional paper. Wearable electronics, such as pagers, computers or multifunction watches, and the like, would be more comfortable to the wearer if the display conformed to the user""s body. Integrated circuit chip cards or smart cards, which have strict flexure life-test performance standards, would be able to incorporate flexible electro-optic displays and still conform to those standards.
In addition to the electro-optic layer and substrate(s), electro-optic displays such as liquid crystal displays (LCDs) require additional layers such as polarizers, analyzers, reflectors, and the like, to achieve the desired electro-optic effect. In applications requiring input by a user, an electro-optic display of any type can also include a touchscreen incorporated into the overall display assembly. Often, electro-optic display assemblies can include a protective barrier layer, an anti-scratch layer, and the like.
Conventionally, all of the layers of the electro-optic display assembly are bonded together by optically-clear adhesives, or other similar means. This results in a laminate having an increased rigidity, in much the same way that bonding multiple thin layers of wood together results in a plywood sheet having significantly enhanced rigidity and strength. Even when the individual layers of the laminate stack are very thin, the overall flexibility of the bonded laminate is still significantly less than the flexibility of a single sheet of plastic having an equivalent thickness. The relatively inflexible mechanical properties of these plastic displays are therefore considered detrimental for performance in applications in which very flexible plastic displays are desirable.
There is a need, therefore, for multiple layer flexible electro-optic displays that have enhanced flexibility.
The invention provides a thin, lightweight, durable electro-optic display assembly that is significantly more flexible than known plastic electro-optic displays, while eliminating the need for additional structural support and shock absorption that glass displays and even rigid plastic displays require. The enhanced flexibility of the electro-optic display assemblies according to the invention is achieved by employing laminate display structures in which there is little, if any, bonding between adjacent layers of the laminate assembly. If any bonding is used, it is localized to areas where stress induced by flexing of the laminate assembly is minimized. As a result, the flexible electro-optic display assemblies according to the invention retain all the advantages of known plastic electro-optic displays, while providing desirably enhanced flexibility.
In one embodiment, the invention provides a flexible electro-optic display assembly that comprises an electro-optic display element that comprises a material having an optical state that changes as a function of an applied electric or magnetic field, at least one laminar layer in sliding apposition to the display element, and optionally one or more additional slidingly apposed laminar layers, wherein the electro-optic display element, the at least one laminar layer and the optional one or more additional laminar layers comprise individual layers of a laminate assembly; and a structure element for fastening together the individual layers of the laminate assembly, wherein the structure element engages a portion of the laminate assembly so as to maintain the individual layers of the laminate assembly in the sliding apposition, wherein upon flexing of the laminate assembly, the individual layers slide relative to each other.
The structure element can comprise a flexible frame structure having an inner periphery defining a viewing area for a liquid crystal display, the flexible frame structure engaging peripheral portions of the laminate assembly so as to maintain the individual layers of the laminate assembly in the sliding apposition, wherein upon flexing of the display assembly, the individual layers slide relative to each other. The resulting flexible electro-optic display assembly can be mounted into any desired device, such as a cellular telephone, computer, watch band, PDA, pager, clock, integrated circuit chip card, or the like. Alternatively, the device itself can provide the flexible frame structure for the laminate assembly, such as by molding a portion of the device over the laminate assembly.
In another embodiment, the invention provides a flexible electro-optic display assembly such as that described in the embodiment above, wherein the structure element, such as a flexible frame structure, has a top surface portion comprising an area for viewing a liquid crystal display, and a body portion, wherein the top portion and the body portion comprise a housing for the laminate assembly so as to maintain the individual layers of the laminate assembly in the sliding apposition, wherein upon flexing of the housing, the individual layers of the laminate assembly slide relative to each other. An exemplary use for this embodiment is an integrated circuit chip card.
In yet another embodiment of the flexible electro-optic display assembly of the invention, the electro-optic display element, the at least one laminar layer and the optional one or more additional laminar layers comprise individual layers of a laminate assembly having a deflection axis. A fastener is provided for fastening together the individual layers of the laminate assembly. The fastener maintains the individual layers of the laminate assembly in a first position relative to one another at the fastener, and wherein upon flexing of the display assembly, the individual layers slide relative to each other in regions outside the fastener.
The flexible plastic electro-optic display assemblies according to embodiments of the invention are especially suitable for, but not limited to, applications such as xe2x80x9celectronic paperxe2x80x9d and the like, wearable electronics, such as computers, multifunction watches, and the like, and other electronic and/or mobile communication device applications, such as cellular telephones, PDAs, pagers, calculators, clocks, integrated circuit chip cards, computers, television sets, combinations of the foregoing, and the like.